Functional assessment of a person's health status, or recuperation after injury, hospitalization and treatment is of primary concern in medicine. Most branches of Medicine, including geriatrics, rehabilitation and physical therapy, neurology and orthopedics, nursing and elder care research studies currently rely on one of three basic strategies: self-report (either in questionnaires, or structured interviews), observational judgment by professionals or family members (such as the Activities of Daily Living [ADL] scales (Katz 1963), and the Instrumental Activities of Daily Living [IADL] scales (Fillenbaum 1985)), or demonstrated performance of specific skills. Despite being considerably useful, one challenge of these approaches is to relate the findings obtained in the physician's office or research laboratory with the person's function at home (Reuben 1995). An implicit assumption is that an individual's functional ability is independent of the environment. Clinical experience suggests that an individual's functional ability is actually environment-specific, since function increases when subjects are in familiar surroundings due to reduced confusion (Kane 1985). The artificial setting of direct observation in a doctor's office or laboratory setting does not allow the observer to determine the effect of environmental barriers such as unfamiliarity or artificiality on function. Moreover, one-time assessment of function does not allow for assessment of variability of functional performance over the course of a day or several days. Further, one-time measurement of function does not allow for assessment of change, and episodic, rather than continuous measurement of function does not permit determination of the rate of change, a parameter which is vitally important in determining the adequacy of certain clinical services and treatments (such as rehabilitation) following functional loss. The accuracy of a prognosis is improved by measuring the rate of change of a patient's condition.
Since there is little correlation between the presence of a certain disease and its impact on an elder's functional abilities, direct assessment of function is an integral part of geriatric care. For example, an octogenarian with systolic hypertension, congestive heart failure, maturity-onset diabetes mellitus, severe osteoarthritis and a past history of hip fracture might be a vigorous, independent community volunteer, or a frail, highly dependent resident of a nursing home (Fried et al. 1997).
Despite a variety of activities of daily living (ADL) tools developed over the last several decades, a consensus exists with regard to the basic components of such functional assessments. Almost all validated scales include measures of dressing, bathing, toileting, transfer and feeding ability (Fleming et al. 1995). ADL scores indicate the degree to which an individual has independent functioning in each of the self-care areas. However, progress in the assessment of function since the early 1960's has not been well implemented in everyday assessment strategies.
Many devices have been invented to continuously measure the activity levels of patients and to assess their functionality, using piezoelectric sensors and accelerometers (such as that of Dynaport). However, these devices measure activity level and do not really discern, measure or assess the activities of daily living or instrumental activities of daily living (IADL) score comprises six questions that correspond to the individual's ability to bathe, dress, use the toilet, move in out of bed, control their bladder or bowels and feed themselves without help. Similarly, IADL score includes five questions that seek information about the individual's ability to get to places that are outside walking distance, go shopping for groceries, prepare meals, do house work and handle finances without help. None of these devices can automatically infer any the above-mentioned activities specifically.